• Paolo Abeni's avatar
    IB/ipoib: move back IB LL address into the hard header · fc791b63
    Paolo Abeni authored
    After the commit 9207f9d4 ("net: preserve IP control block
    during GSO segmentation"), the GSO CB and the IPoIB CB conflict.
    That destroy the IPoIB address information cached there,
    causing a severe performance regression, as better described here:
    
    http://marc.info/?l=linux-kernel&m=146787279825501&w=2
    
    This change moves the data cached by the IPoIB driver from the
    skb control lock into the IPoIB hard header, as done before
    the commit 936d7de3 ("IPoIB: Stop lying about hard_header_len
    and use skb->cb to stash LL addresses").
    In order to avoid GRO issue, on packet reception, the IPoIB driver
    stash into the skb a dummy pseudo header, so that the received
    packets have actually a hard header matching the declared length.
    To avoid changing the connected mode maximum mtu, the allocated
    head buffer size is increased by the pseudo header length.
    
    After this commit, IPoIB performances are back to pre-regression
    value.
    
    v2 -> v3: rebased
    v1 -> v2: avoid changing the max mtu, increasing the head buf size
    
    Fixes: 9207f9d4 ("net: preserve IP control block during GSO segmentation")
    Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    fc791b63
ipoib_ib.c 31.9 KB